A storage system refers to a system composed of various storage devices for depositing programs and data, control members, and devices and algorithms for managing information scheduling. When the storage system includes a plurality of magnetic disk drives (or shortly referred to as a “magnetic disk”), part of magnetic disk drives are usually used for storing system information of the storage system which is used by the storage system per se. This part of magnetic disk drives is referred to as “system disk drives” (or shortly referred to as a “system disk”) herein. In contrast, the remaining disk drives used by a user to store data are referred to as “user disk drives” (or shortly referred to as a “user disk”). As the system disk stores information related to system, the system disk are crucial to running of the storage system. Therefore, it has become one of hot topics in the field of storage systems regarding management of a system disk and how to recover a system disk and then recover the storage system from a failure when the system disk fails.
Currently, a redundant array of independent disks (hereinafter shortly referred to as “RAID” or “disk array”) is widely applied to system disks that manage a storage system, which prevents data loss caused by failure of the disk or storage device by using redundancy of data and device. Dependent on different needs of protection degrees, different RAID levels are defined, for example, RAID 0, RAID 1, RAID 3, RAID 5, RAID 6, RAID 10, triple mirror and the like. However, if the number of failed system disks is too large (for example, for RAID 3 or RAID 5, two system disks fail), the system disk data cannot be recovered relying on the redundancy of the RAID, even if the RAID is used to manage system disks. In this case, the practice in the prior art is always returning the system disks to the manufacturers and re-mirroring the system disks to an initial state. The consequence is that all data in the array will be lost and the system will return to an out-of-factory default state, which not only increases costs but also is inefficient.